Jud - s/v Sputnik
Super Anarchist
Here’s a good one - lots to chew on here:
Acutal use of celestial navigation prior to the GPS era
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Jud - s/v Sputnik
Super Anarchist
Here’s another one - but it’s not actual use of celestial prior to the GPS era, it’s the right now era (literally right now). Jeremy Bagshaw has been at sea almost 9 months solo (almost) non-stop, navigating solely with a sextant, so has likely gotten pretty good at it.
MagentaLine
Super Antichrist
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Still refresh my memory every couple of years...
Israel Hands
Super Anarchist
^^Tom's book is a good one for helping envision the way it works, for those of us who came late to this practice and are duffers.
Slim
Super Anarchist
Talchotali
Capt. Marvel's Wise Friend
I have unscientifically noted that most long-term celestial navigators have serious glaucoma or other issues in one eye late in life from shooting the sun.
Not using good filters or poor technique?
Not using good filters or poor technique?
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Thanks for that Jud.
Jeremy is using my Zeiss sextant which I had lent him for the voyage!
I'm looking forward to getting it back and hearing all the stories.
Regards.
El Borracho
Bar Keepers Friend
The Apollo situation sure solved two of the problems facing sailors: A stable platform and clear skies. The horizon gets far away though. Horizons?
Cisco
Super Anarchist
Check the scale of the chart. If those are three genuine sights that isn't too bad, especially if the NW/SSE pair are 'back to back' . A shame the navigator didn't get another 'back to back' with the one that has a NE?SW azimuth.Navigation : the Art of knowing where you are not ......
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Getting 'back to back' sights lets you see , amongst other things , if there is any dodgy refraction around, esp in very hot or cold locations.
One thing that is quite important when taking stars on a fast moving ship is running up each position line to a common time. Still of consequence if you take 20 minutes over stars on a yacht doing -say- ten knots.
mckenzie.keith
Aspiring Anarchist
When I moved my boat from Monterey to Santa Cruz we were so sopped in with fog that we couldn't see Santa Cruz harbor until we were a few hundred yards away and then we were like OH, there is the light house. Thank god for GPS. We would have had to steer for Live oak and then turn left and follow a depth countour or something in pre-GPS days.
Panoramix
Super Anarchist
.... or wait for 3, 6, 12, 24 hours or more while your DR is becoming dodgier and dodgier!
tane
Super Anarchist
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though never doing 10kn, I used to shoot stars approximately abeam first, & ahead or astern last...in those days... now long gone...
paps49
Super Anarchist
So you keep a wide berth.
tane
Super Anarchist
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...not if you want to anchor there...
paps49
Super Anarchist
I was thrown in at the deep end, semi Shanghaid onto a Taiwan Turkey (Hudson Force 50) out of Manila bound for LA via great circle.
Two days out it became obvious the owner couple had no idea, they couldn't get within 100 miles of each other.
Off watch I desperately scanned the nav books on board but I couldn't quite grasp it. Finally thank Christ I found a sun sights for dummies or some thing similar and the penny dropped.
The sun is a duck, shoot the duck and it falls straight down to the surface, you can measure that. The angle gives you a cone, you are somewhere on this circle. It made sense.
We made landfall close enough and all was well.
Two days out it became obvious the owner couple had no idea, they couldn't get within 100 miles of each other.
Off watch I desperately scanned the nav books on board but I couldn't quite grasp it. Finally thank Christ I found a sun sights for dummies or some thing similar and the penny dropped.
The sun is a duck, shoot the duck and it falls straight down to the surface, you can measure that. The angle gives you a cone, you are somewhere on this circle. It made sense.
We made landfall close enough and all was well.
It's very difficult or impossible in practice to get better than 10nm accuracy with a sextant from the deck of a small boat. Anybody telling you otherwise is overconfident and underexperienced. You can however fix your latitude with slightly better accuracy at noon as the errors of timekeeping are gone. Hence the practice of latitude sailing, where you simply sail along the latutude of the intended landfall from dawn and keep a good lookout. From the masthead if necessary. The horizon from the deck of a yacht is not further than 3 miles away. From the masthead, or even the spreaders it's considerably further. Then there is the reflection of bright azure shallow water on the underside of typical tropical cumulus clouds, known as "blink". This can be seen from 20 miles.
El Borracho
Bar Keepers Friend
Some famous sailing of yore book says that ships would loiter for weeks off the California coast waiting for navigable weather to enter harbors (Dana?). The GC crossing from Asia to NA is famous for a continuous overcast that entirely precludes celestial sights. The NA continent was located by creeping SE’ward watching for littoral creatures and such.
I’ve completely abandoned celestial. I think those that relish the chore might instead bring a seabag full of old grocery receipts to add up, checking the arithmetic, so to while away the hours.
